A PlanarImage wrapper for a non-writable
RenderedImage. The tile layout, sample model, and so forth
are preserved. Calls to getTile(), getData(),
and copyData() are forwarded to the image being adapted.

The set of properties available on the image will be a combination of
those defined locally via setProperty() and those defined
on the source image with the local properties taking precedence. No
PropertySourceChangeEvent will be generated as a result of
changes to the property set of the source image.

From JAI's point of view, this image is a PlanarImage of
unknown type, with no sources. The source image is assumed to be
immutable. If the RenderedImage source implements
WritableRenderedImage, a
WritableRenderedImageAdapter should be used.

The methods are marked 'final' in order to allow dynamic inlining to
take place. This should eliminate any performance penalty associated with
the use of an adapter class.

Since the methods of this class all derive from
PlanarImage, they are not commented in detail.